Cody, you have to patent your idea about EQ.

[Anonymous]

Cody, you have to patent your idea about EQ. Otherwise it will be taken by Minelab. If they insert simple filter with a switch inside headphones it will be great and cheap and very simple improvement. As I remember from school such filter for may be 1kHz compares of a small inductor and couple capacitors and could be easily put in tandem with headphones. It is really cheap and very helpful for those who does not like constant metal low sounds ( do not know anybody ). The main point is to hunt in All Metal with sound ( not metal) discrimination and to free processor and this will give more important sweep speed as well. I will ask my friend engineer to measure the metal frequencies maybe 1-2kHz and develop a good filter. Hope that it will not be big time constant ( TC) for the filter, similar to

 

[Anonymous]

I have messed arond with this and it can be done with a variable capacitor. I put one in a set of headpnones for a tone control and then put a knob so the tone can be adjusted similar to the volume control. I thought an EQ would be better for more control and since they sell an EQ that will do this for bout $40 will get one and see how it works. The variable capacitor in the headphones will have an effect on the high tones and I would like to kick them up. You are correct in that a switch if done in heaphones is needed to slip to normal or ferrous.
Your english is fine and I have notice you post before and wondered who you were as you conduct yourself so well.
HH, Cody

 

[Anonymous]

To tell the truth I never saw a variable capacitors except in old radios for tuning. When studied in navy school as sparks , as a fun we developed small sound amplifiers and somebody ( not me ) EQs. I recall that if we want to cut frequency range from 1kHz to 10kHz a capacitor of approx 0.05 mkf will be OK. But for a very narrow range of 50-70 Hz ( low sound ) I think it is impossible to use just one capacitor. It should be three capacitors at least and an inductor as well. I could find the relevant circuitry for 50-100Hz filter with formula to count the components but not now since I am abroad in business trip and return home in summer.
In case of small musical EQ I think it will not be sufficient quality because the filter is just reducing the tones without cutting off and in this device we can use only the very first slider for low tones. If connect to any tape recorder or even better to sound amplifier with good EQ we could have an idea. There are professional EQs where it is possible to cut out any range but this is not our case, just for experimenting. To my mind the best is to cut out exact band ( 50-100 Hz may be ) and to start from copper tones

 

[Anonymous]

I was really thinking of a variable resistor and fixed capacitor which is what I used for the tone control in the headphones. They make variable capacitors that are very small.
Now days you only see inductors used for the most part in more expensive analog equipment. It is common to use digital filters that can be adjusted with a digital control.
I used a singel variable resistor and fixed capacitor in the headphone. They work well but only in a narrow frequency range. I have not gone any further with that thinking I would try a small EQ. I have an EQ that is large so know It works but want a small one that I can plug in the output of the detector.
HH, Cody

 

[Anonymous]

It is clear now. I was told by my friend that this could be solved by including two capacitors and resistor ( double filter ) before the low frequency amplifier inside the circuitry of EXPII and this will start to cut from lowest frequency to middle ( abt 3dB ). Very simple. Also to solve possible delay in filter better to use FAST or replace one capacitor inside. Could be found out by experiments. It